Identification of GlcNAcylation sites of peptides and alpha-crystallin using Q-TOF mass spectrometry

The addition of a single N-acetylglucosamine residue O-linked to serine and threonine residues of nuclear and cytoplasmic proteins is a widespread mod ification throughout all eukaryotes. The conventional method for detecting and locating sites of modification is a multi-step radioactivity-based prot ocol. In this paper we show that using quadrupole time-of-flight (Q-TOF) ma ss spectrometry, modification sites can be identified at a significantly hi gher sensitivity than previous approaches. This is the first demonstration that sites of O-GlcNAcylation can be identified directly using mass spectro metry. (C) 2001 American Society for Mass Spectrometry.